A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disk having magnetic surfaces. When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read/write head that is positioned over a specific location of a disk by an actuator. A read/write head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. Write heads make use of the electricity flowing through a coil, which produces a magnetic field. Electrical pulses are sent to the write head, with different patterns of positive and negative currents. The current in the coil of the write head induces a magnetic field across the gap between the head and the magnetic disk, which in turn magnetizes a small area on the recording medium.
The nature of magnetic-recording media fabrication is such that the media typically have micro-scale defects, such as asperities and pits in the outer surface of the media. Such defects can cause errors with writing operations, and therefore also reading operations, because the data cannot always be written properly over the asperities and pits. Therefore, the disk media are typically tested at the factory during HDD manufacturing in order to identify any defective areas of the disk. However, the time currently required to run these disk defect tests is non-trivial. Further, factory process time is an important resource, so managing the use of process time is a common goal in manufacturing.
Any approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.